A progress in an electronic display as man machine interface has resulted in popularization of an interactive input system. Among others, an apparatus having a touch screen (a digitizer) and an associated display is widely used in various fields such as an ATM (automated teller machine), a merchandise management, an outworking (canvassing, selling), a guide sign, and an entertainment device. Use of the touch screen in combination with a lightweight and thin display (e.g., a liquid crystal display) dispenses with any keyboard and exhibits the features of the display, and thus such a touch screen display is increasingly used for mobile devices. The touch screen display is a device for inputting (or feeding) information or instructions to a computer by touching a prescribed area on a touch screen (or a touch sensitive panel) with an input means such as a finger or a pen (a digital pen or a stylus). According to the position detection method, the touch screen display can be classified into an optical system, an ultrasonic-wave system, a capacitive system, a resistive system, and other systems. Among these systems, the capacitive system detects the location of the touch using a change in capacitance. Considering excellent functionality, a projected capacitive touch screen display of ITO grid system is now being used for mobile devices and is receiving a lot of attention. The mobile devices include a smartphone, a mobile phone, an electronic paper, a tablet personal computer (PC), a pen tablet (or a graphics tablet), and a game console. Among the capacitive touch screen displays, a pen-input touch screen display which uses a pen as an input means, is also now being widely used and being increasingly applied for a smartphone, an electronic paper, a tablet PC, a pen tablet, a game console, and a PC. The display of the touch screen display is provided with, on a surface thereof, a hardcoat film, an anti-Newton-ring film, a soft film, or other films according to purposes. Nowadays, a pen-input tablet (or a pen tablet) as a pointing device for computer is also in widespread use. The pen tablet and the above-mentioned touch screen display are referred to as a pen-input device. Moreover, the following are also developed: a high-resolution (4K) touch screen television having a pixel dimension (or pixel number) four times as large as that of a full high-definitions television, and a high-resolution pen-input device that is used in the architectural field or the medical field. For these devices, a high transparency is also required. As pen-input devices are widely used for various purposes, these devices require higher functions for a comfortable writing experience (or writing comfort) in pen input (or an input operation with a digital or stylus pen).
Japanese Patent Application Laid-Open Publication No. 2010-153298 (JP-2010-153298A, Patent Document 1) discloses a transparent conductive laminate film for a touch screen; the laminate film is excellent in touch feeling with a finger and comprises, in sequence, a hardcoat layer, a substrate consisting of a polyester film, and a transparent conductive layer consisting of a metal oxide; the hardcoat layer has an average area surface roughness of 0.08 to 0.30 μm, an average friction coefficient MIU of KES surface friction characteristic value of 0.13 to 0.17, and a fluctuation MMD of friction coefficient of 0.006 to 0.015.
However, in this document is also described neither a pen-input touch screen nor a comfortable writing experience in pen input. Furthermore, use of this laminate for a touch screen would offer an uncomfortable writing experience in pen input, which is far from a comfortable writing experience such as a pencil writing experience.
Japanese Patent Application Laid-Open Publication No. 2014-97649 (JP-2014-97649A, Patent Document 2) discloses a transparent film for use on a display of a pen-input touch screen with an improved comfortable writing experience in pen input on a surface of the display; the transparent film contains a transparent substrate film and a coat layer disposed on at least one side of the transparent substrate film and has a total light transmittance of not less than 85% in accordance with Japanese Industrial Standards (JIS) K7136, and the coat layer has a surface texture with a maximum height of rolling circle waviness profile (WEM) in accordance with JIS B0610 of not less than 15 μm.
Unfortunately, the transparent film offers an improved comfortable writing experience in pen input, while the film wears out a pen tip severely. If the comfortable writing experience in pen input is controlled by an uneven surface profile (or texture) of the film, the pen tip would easily be worn off due to the uneven profile. Thus, the comfortable writing experience in pen input and the reduced abrasion (or wear) of the pen tip are in a trade-off relationship, and it is difficult to achieve compatibility.